Image display device

ABSTRACT

At least one exemplary embodiment is directed to an image display device which includes: a first TN liquid crystal modulator for modulating the polarization state of first colored light; a second TN liquid crystal modulator for modulating the polarization state of second colored light; a third TN liquid crystal modulator for modulating the polarization state of third colored light; and an optical system for synthesizing the image light emitted from the three liquid crystal modulators; where a first voltage is applied to the first liquid crystal modulator for providing the first colored light with about half-wavelength phase difference; second voltage higher than the first voltage is applied to the second liquid crystal modulator for providing the second colored light with about half-wavelength phase difference; and third voltage higher than the second voltage is applied to the third liquid crystal modulator for providing the third colored light with about half-wavelength phase difference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image display device, andspecifically, though not exclusively, relates to image modulation usingliquid crystal modulators.

2. Description of the Related Art

Hitherto, conventional liquid crystal modulators, such astwo-dimensional pixel optical switches, that can serve as an imagemodulation device used in a projection-type image display device, andliquid crystal projectors using such liquid crystal modulators. Of theliquid crystal modulators used in a liquid crystal projector, there areso-called TN (Twisted Nematic) liquid crystal modulators for example.The TN liquid crystal modulators are a configuration where nematicliquid crystals, which have positive dielectric anisotropy, is sealedbetween a first transparent substrate having a transparent electrode anda second transparent substrate having transparent electrodes, wiring,and switching devices which form pixels. The major axis of liquidcrystal molecules can be twisted 90 degrees continuously between the twotransparent substrates.

Also, other than such transmissive liquid crystal modulators, there arereflective liquid crystal modulators which have a reflective mirrorinside one of the substrates as a two-dimensional pixel optical switch.

Liquid crystal modulators use an ECB (Electrically ControlledBirefringence) effect, and are used to control the polarization stateand form an image. Of these, the liquid crystal modulators generallyused are those in TN mode operation, where the nematic liquid crystalsof which dielectric anisotropy is positive are homogeneously alignedspirally, and where optical switching is performed with liquid crystalbirefringence.

In the event that TN mode is used and modulation is controlled with theECB effect, in a state where there is no voltage applied to a liquidcrystal layer, the liquid crystal molecules which differ in refractiveindex in the diameter direction (minor axis direction) and the liquidcrystal molecule major axis can be arranged in an approximately 90degree twisted spiral on a plane which is roughly perpendicular to thethickness direction of the liquid crystal layer. Therefore the liquidcrystal layer has birefringence as to a predetermined direction of theplane, applies retardation (optical path difference between two lightfluxes with differing polarization direction) as to a light wave whichtransits through the liquid crystal layer, and effects change to thepolarization of the light wave.

With a general liquid crystal modulator design, incident light ischanged to a linearly polarized state with light wave polarization in apredetermined direction, by a polarization control device such as apolarizer. Then the obtained light wave is cast into the liquid crystallayer, and when the linearly polarized light which oscillates in thispredetermined direction transits through the liquid crystal layer, onlya half-wavelength of retardation is applied to the incident lightwavelength (e.g., a center-wavelength in a given light wavelength band).

The light having transited through the liquid crystal layer has theoscillating direction changed to the direction at right angles with(perpendicular to) the oscillating direction of the linear polarizationbefore the light being cast in, and the light is emitted.

After this, the polarization state is selected by the polarizationcontrol device positioned on the incidence side and by positioning apolarization control device such as the polarizer which is in a crossedNichols arrangement on the emitting side, and the selected lighttransmits through the polarization control device.

With this design, when voltage is applied to the liquid crystal layer,using ECB effects, the liquid crystal molecules tilt the molecule majoraxis direction thereof in the thickness direction of the liquid crystallayer, and the amount of birefringence in the liquid crystal layerthickness direction is lessened. Thus, the light wave having transitedthe liquid crystal layer changes to an elliptic polarization stateaccording to voltage applied to the liquid crystal layer. The lightcomponents where the oscillating direction is not orthogonallytransformed are interrupted, by the polarization control devicepositioned on the light emitting side. Thus, the device is configured sothat the intensity of the incident light is modulated.

The basic operation principles of the liquid crystal modulators will bedescribed using FIG. 5 and FIG. 6.

FIG. 5 is an operation description diagram of a case of using atransmissive liquid crystal modulator. In FIG. 5, the light from a lightsource (not shown) becomes linearly polarized light LIW via apolarization selector such as a polarizer not shown, and is cast into atransmissive liquid crystal modulator 300 with the polarized light fromthe arrow IW direction at a 45 degree angle with the orientationdirection of the liquid crystal of the transmissive liquid crystalmodulator 300.

In this event, the incident light LIW divides the liquid crystal layerof the transmissive liquid crystal modulators 300 into twocharacteristic modes and is propagated. The emitted light LOW is emittedin the direction of the arrow OW in the diagram, with the retardationδ(λ) shown in the following Expression (1) between the twocharacteristic modes.δ(λ)=2π(d·Δn)/λ  (1)

Here, λ is the wavelength of the incident light LIW, d is the thicknessof the liquid crystal layer, and Δn is the refractive index anisotropyof the liquid crystal layer.

Next, the light LOW transits a polarization selecting device 301 such asa polarizer, which transmits linearly polarized light which isorthogonal to the polarization direction of the incident light LIWpositioned on the emitting side. In this event, the transmissive liquidcrystal modulators 300 are transmitted, and the amount of lighttransmitting the polarization selecting device 301, that is to say, thetransmittance T(λ) of the transmissive liquid crystal modulators 300 areas follows.

If the transmittance of the polarization selecting device 301 is 100% asto the linearly polarized light to be transmitted, and the apertureratio of the transmissive liquid crystal modulator 300 is 100%, and thenon-polarized transmittance is 100%, then the transmittance T(λ) of thelight LMW emitted in the MW arrow direction in the diagram whichtransits the polarization selecting device 301 as to the phasedifference δ(λ) is expressed byT(λ)=0.5(1−cos(δ(λ)))  (2)

The transmittance of the liquid crystal modulators hereafter refers tothe ratio of amount of light which transits the polarization selector301 to the amount of light of the linearly polarized light cast into theliquid crystal modulators 300, via the polarization selectors asexpressed in Expression (2).

When voltage is applied to the liquid crystal layer, the liquid crystalmolecules move in the direction from parallel to perpendicular as to thesandwiched substrate of the liquid crystal layer, and thus therefractive index anisotropy Δn appears to be reduced. Therefore theretardation δ(λ) is reduced, and when δ=0 the transmittance T=0, and ablack display is realized.

On the other hand, with no voltage applied, the refractive indexanisotropy Δn is at its greatest, and if the liquid crystal layerthickness d and the refractive index anisotropy Δn of the liquid crystallayer is determined such that d·Δn=λ/2, then δ(λ)=π, the transmittanceis T=1, and the display is brightest.

FIG. 6 is an operation description diagram using reflective liquidcrystal modulators. In FIG. 6, the light LIW from the light source iscast into the polarizing beam splitter 401 from the IW arrow directionin the diagram, the light LIWB of the P components transit thepolarizing selector film 401 a in the IWB arrow direction in thediagram, and the light LIWA of the S components are reflected anddeflected in the IWA arrow direction in the diagram. The light componentLIWA of the arrow IWA includes the light selected which is linearlypolarized in the vertical direction in the diagram.

The liquid crystal orientation direction of the reflective liquidcrystal modulators 400 is tilted at a 45 degree angle as to the linearlypolarized direction of the light LIWA. The light LIWA cast into thereflective liquid crystal modulators 400 from the IWA arrow directiondivides the liquid crystal layer of the reflective liquid crystalmodulators 400 into two characteristic modes that are propagated. Thenwhen the light LOW is reflected and emitted in the direction of thearrow OW in the diagram. The light LOW is emitted with the retardationδ(λ) between the two modes, expressed in the following Expression (3).δ(λ)=2π(2d·Δn)/λ  (3)

Here, λ is the wavelength of the incident light, d is the thickness ofthe liquid crystal layer, and Δn is the refractive index anisotropy Δnof the liquid crystal layer.

Then, the light LOW emitted in the OW arrow direction in the diagram,the light LBW of the vertical direction component (S-polarizationcomponent as to the polarizing beam splitter 401) is reflected in the BWarrow direction in the diagram by the polarization separation plane 401a and returns to the light source side, and the light LMW of theparallel direction component (P-polarization component as to thepolarizing beam splitter 401) is transmitted in the MW arrow directionin the diagram by the polarization separation plane 401 a. The amount oflight which reflects from the reflective liquid crystal modulators 400and transmits through the polarizing beam splitter 401, that is to say,the reflectivity R(λ) of the reflective liquid crystal modulators 400can be expressed as follows. If the S-polarizing reflectivity of thepolarizing beam splitter 401 is 100%, the P-polarizing transmittance is100%, and the aperture ratio of the reflective liquid crystal modulators400 is 100% and the non-polarizing reflectivity is 100%, then thereflectivity (light transfer rate) R(λ) emitted in the MW arrowdirection in the diagram as to the retardation δ(λ) is expressed asR(λ)=0.5(1−cos δ(λ)))  (4)

The reflectivity of the reflective liquid crystal modulators refers tothe ratio of amount of light which transits the polarizing beam splitter401 as to the amount of light of the linearly polarized light cast intothe liquid crystal modulators 400, via the polarizing beam splitter 401a as expressed in Expression (4).

When voltage is applied to the liquid crystal layer, the liquid crystalmolecules move in the direction from parallel to perpendicular as to thesandwiched substrate of the liquid crystal layer, and thus therefractive index anisotropy Δn appears to be reduced. Therefore theretardation δ(λ) is reduced, and when δ=0 the reflectivity R=0, anddisplay becomes black.

On the other hand, with no voltage applied, the refractive indexanisotropy Δn is at its greatest, and if the liquid crystal layerthickness d and the refractive index anisotropy Δn is determined so that2d·Δn=λ/2, then δ(λ)=π, the reflectivity is R=1, and the display isclearest.

With the liquid crystal modulators which perform modulation controlusing the ECB effect control in this TN mode, there are restrictionsregarding the light wavelength λ and amount of applied retardation whichindicates the absolute amount of the length not dependent on the lightwavelength of the retardation δ. According to the principles describedabove, it is apparent that the phase difference δ is an amount dependenton the wavelength. In other words, the wavelength band of the incidentlight of the three primary colors each have a wavelength band of R, G, B(red, green, blue), and the wavelength band has a width of slightly lessthan 100 nm.

Therefore, the TN-type liquid crystal modulators designed with apredetermined standard are configured so as to apply retardation of onlya half-wavelength as to the predetermined wavelength light in a statewith no voltage being applied to the liquid crystal layer. Thus, withthe wavelength band of slightly less than 100 nm corresponding to eachcolor, it is inevitable that retardation of greater than ahalf-wavelength can be applied, or retardation of less than ahalf-wavelength can be applied.

One more related restriction is that, because the TN mode is used, thebirefringence of the liquid crystal layer is greatest when no voltage isbeing applied to the liquid crystal layer, and while the amount ofretardation can be controlled in the direction of lessening by the ECBeffect control, the opposite direction of increasing the amount ofretardation is impossible.

On the other hand, a mainstream configuration is a full-color displaytype projection display device (color projector) which can use a liquidcrystal modulator as a two-dimensional pixel optical switch whichmodulates the colored lights RGB (red, green, blue) which are the threeprimary colors of the additive color-mixing display as individualtwo-dimensional images, regardless of the transmissive liquid crystalmodulators or reflective liquid crystal modulators, and after this, thefull-color image is displayed using light-synthesizing means. This colorproject has a configuration of using three liquid crystal modulators,for modulating each of the R, G, and B light.

A color projector using such three liquid crystal display devices hasbeen described in EP1447993A1.

SUMMARY OF THE INVENTION

At least one exemplary embodiment is directed to an image-displaydevice, where a modulated image is generated by polarizing an imagepattern with liquid crystal modulators, converting this to an intensitymodulated image with a polarization selecting device which selects apolarization state, and enlarging and projecting this onto a projectionobject.

Accordingly, At least one exemplary embodiment is directed to an imagedisplay device which can prevent color balance distortion or lightfalloff, or lessen the degree thereof, by having the applied retardationfrom the liquid crystal modulators in a state with no voltage applied todiffer for each color of the RGB (this is not restricted to the threecolors RGB, but can be applied to a configuration where four or morecolors are synthesized).

A first exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where a firstvoltage is applied to the first liquid crystal modulator forhalf-wavelength retardation of the first colored light; a second voltagewhich is higher than the first voltage is applied to the second liquidcrystal modulator for half-wavelength retardation of the second coloredlight; a third voltage which is higher than the second voltage isapplied to the third liquid crystal modulator for half-wavelengthretardation of the third colored light.

A second exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where theretardation which the second liquid crystal modulator applies to thesecond colored light without applying voltage is greater than theretardation which the first liquid crystal modulator applies to thefirst colored light without applying voltage; and the retardation whichthe third liquid crystal modulator applies to the third colored lightwithout applying voltage is greater than the retardation which thesecond liquid crystal modulator applies to the second colored lightwithout applying voltage.

A third exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where theretardation which the first liquid crystal modulator applies to thefirst colored light without applying voltage is about the same as theretardation which the second liquid crystal modulator applies to thefirst colored light without applying voltage; and the retardation whichthe first and second liquid crystal modulator applies to the firstcolored light without applying voltage is greater than the retardationwhich the third liquid crystal modulator applies to the first coloredlight without applying voltage.

A fourth exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where theretardation which the first liquid crystal modulator applies to thefirst colored light without applying voltage is greater than theretardation which the second liquid crystal modulator applies to thefirst colored light without applying voltage; and the retardation whichthe second liquid crystal modulator applies to the first colored lightwithout applying voltage is about the same as the retardation which thethird liquid crystal modulator applies to the first colored lightwithout applying voltage.

A fifth exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where a firstvoltage is applied to the first liquid crystal modulator forhalf-wavelength retardation of the first colored light; a second voltagewhich is lower than the first voltage is applied to the second liquidcrystal modulator for half-wavelength retardation of the second coloredlight; a third voltage which is lower than the second voltage is appliedto the third liquid crystal modulator for half-wavelength retardation ofthe third colored light.

A sixth exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where theretardation which the second liquid crystal modulator applies to thesecond colored light without applying voltage is less than theretardation which the first liquid crystal modulator applies to thefirst colored light without applying voltage; and the retardation whichthe third liquid crystal modulator applies to the third colored lightwithout applying voltage is less than the retardation which the secondliquid crystal modulator applies to the second colored light withoutapplying voltage.

A seventh exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where theretardation which the first liquid crystal modulator applies to thefirst colored light without applying voltage is about the same as theretardation which the second liquid crystal modulator applies to thefirst colored light without applying voltage; and the retardation whichthe first and second liquid crystal modulator applies to the firstcolored light without applying voltage is less than the retardationwhich the third liquid crystal modulator applies to the first coloredlight without applying voltage.

An eighth exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where theretardation which the first liquid crystal modulator applies to thefirst colored light without applying voltage is less than theretardation which the second liquid crystal modulator applies to thefirst colored light without applying voltage; and the retardation whichthe second liquid crystal modulator applies to the first colored lightwithout applying voltage is about the same as the retardation which thethird liquid crystal modulator applies to the first colored lightwithout applying voltage.

A ninth exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where in astate where the same voltage is applied to the three liquid crystalmodulators, the three liquid crystal modulators are configured to applythe same retardation as to light of the same wavelength; the amount ofretardation at the time there is no voltage applied to the three liquidcrystal modulators equates to a half-wavelength of approximate centerwavelength of the first colored light; the second and third liquidcrystal modulators apply retardation equivalent to a half-wavelength ofapproximate center wavelength of the second and third colored lights, byapplying a predetermined voltage on each of the liquid crystalmodulators.

A tenth exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where in astate where a predetermined voltage is applied, the first and secondliquid crystal modulators are configured to apply the same predeterminedretardation as to light of a predetermined wavelength; and in the statewhere the predetermined voltage is applied, the retardation which thethird liquid crystal modulator applies as to light of the predeterminedwavelength differs from the predetermined retardation; the amount ofretardation at the time there is no voltage applied to the first liquidcrystal modulator equates to a half-wavelength of approximate centerwavelength of the first colored light; the amount of retardation at thetime there is no voltage applied to the third liquid crystal modulatorequates to a half-wavelength of approximate center wavelength of thethird colored light; and in order to apply the retardation equating to ahalf-wavelength of approximate center wavelength of the second coloredlight, a voltage greater than 0 (zero) is applied to the second liquidcrystal modulator.

An eleventh exemplary embodiment is directed to an image display devicewhich includes: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators; where in astate where a predetermined voltage is applied, the second and thirdliquid crystal modulators are configured to apply the same predeterminedretardation as to light of a predetermined wavelength; and in the statewhere the predetermined voltage is applied, the retardation which thefirst liquid crystal modulator applies as to light of the predeterminedwavelength differs from the predetermined retardation; the amount ofretardation at the time there is no voltage applied to the first liquidcrystal modulator equates to a half-wavelength of approximate centerwavelength of the first colored light; the amount of retardation at thetime there is no voltage applied to the second liquid crystal modulatorequates to a half-wavelength of approximate center wavelength of thesecond colored light; and in order to apply the retardation equating toa half-wavelength of approximate center wavelength of the third coloredlight, a voltage greater than 0 (zero) is applied to the third liquidcrystal modulator.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram for describing a drive state of atransmissive liquid crystal modulator according to an exemplaryembodiment of the present invention.

FIG. 2 is a schematic diagram for describing a drive state of atransmissive liquid crystal modulator according to the exemplaryembodiment.

FIG. 3 is a schematic diagram for describing a drive state of areflective liquid crystal modulator according to the exemplaryembodiment.

FIG. 4 is a schematic diagram for describing a drive state of areflective liquid crystal modulator according to the exemplaryembodiment.

FIG. 5 is a schematic diagram for describing the operation of atransmissive liquid crystal modulator.

FIG. 6 is a schematic diagram for describing the operation of areflective liquid crystal modulator.

FIG. 7 is a diagram illustrating light wavelength distribution of thelight incident to the liquid crystal modulators.

FIG. 8 is a schematic diagram of the main portions of a projection-typedisplay device using a transmissive liquid crystal modulator accordingto an exemplary embodiment of the present invention.

FIG. 9 is a schematic diagram of the principal portions of aprojection-type display device using a reflective liquid crystalmodulator according to an exemplary embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The following description of at least one exemplary embodiment is merelyillustrative in nature and is in no way intended to limit the invention,its application, or uses.

Processes, techniques, apparatus, and materials as known by one ofordinary skill in the relevant art may not be discussed in detail butare intended to be part of the enabling description where appropriate,for example the fabrication of liquid crystal modulators.

In all of the examples illustrated and discussed herein any specificvalues, for example phase differences. Thus, other examples of theexemplary embodiments could have different values.

Notice that similar reference numerals and letters refer to similaritems in the following figures, and thus once an item is defined in onefigure, it may not be discussed for following figures.

With the present exemplary embodiment, a method/device is discussed forfacilitating the improvement of color balance distortion (light falloffof a specific color) or light falloff, or for lessening the degree ofcolor balance distortion or light falloff, in the event that the sameliquid crystal modulators are used for the 3 colors RGB.

Here, liquid crystal modulators which are conventionally configured tobe the same can be used as modulators of each RGB-color light, and whenretardation of half wavelength is applied to the light wavelength in theproximity of the center-of-gravity wavelength (center wavelength of awaveband) of the green color (G) which has the highest visibilityfeature (easiest for the human eye to see). In other words, whenretardation of a substantial portion (e.g., all) of the liquid crystalmodulators are designed to match the light of the wavelength, which canhave the highest visibility, the following problems can occur. Forexample, an appropriate amount of retardation (half wavelength here) canbe applied to the G (green) colored light, but even for the R (red)colored light the retardation amount applied becomes less than halfwavelength even in a state without voltage applied, and this results inthe R (red) color in the image displayed having light falloff.

Thus, the following solution can be considered. For an image displaydevice (liquid crystal display device), liquid crystal modulatorsspecific to each color are prepared as liquid crystal modulators whichmodulate each RGB-color, and the retardation amount to be applied toeach color light liquid crystal modulator is appropriately set. However,in this case, liquid crystal modulators which have differentspecifications for each RGB-color must be manufactured, and thereforethe manufacturing process can become a major issue.

Therefore, with the present exemplary embodiment, a device configured asa liquid crystal display device for G (green) wavelength use, ispositioned in the G-color light path and the B-color light path. Thusconfigured, voltage applied to the liquid crystal layer of the liquidcrystal modulators positioned in the B-color light path can be adjusted(here, the voltage applied to the liquid crystal modulators positionedin the B-color light path can be higher than the voltage applied to theliquid crystal modulators positioned in the G-color light path), and bydoing so, the brightness of the B (blue) color is adjusted. Thus, theG-color and the B-color can obtain the appropriate amount of light.Additionally, the liquid crystal modulators to be positioned in theR-color light path can be liquid crystal modulators which differ fromthe liquid crystal modulators positioned together in the G-color lightpath and the B-color light path as described above. In other words, byliquid crystal modulators which have appropriately set retardationamounts to be applied to the R-color light, that is to say, liquidcrystal modulators such that the retardation amount applied to thecenter-of-gravity wavelength of R-color light is half wavelength with novoltage applied, being positioned in the R-color light path, the R-colorlight in the colored image can be set to the appropriate brightness.

In other words, with the present exemplary embodiment, a liquid crystaldisplay device will be specifically described which can display an imagewith little loss of R-color light (and/or B-color light) as compared tothe case where the same liquid crystal modulators can be positioned inthe light paths of a substantial portion (e.g., all) of the RGB-colorlight, and a substantial portion (e.g., all) of the liquid crystalmodulators can be controlled in the same way matching thecenter-of-gravity wavelength of G-color light.

The drive control of the liquid crystal modulators used in the liquidcrystal display device of the present exemplary embodiment will bedescribed below with reference to FIG. 1 through FIG. 4.

The present exemplary embodiment can use, for example, TN (TwistedNematic) mode action liquid crystal modulators with positive nematicphase. These are liquid crystal modulators where the refractive index inthe major axis direction of the liquid crystal molecules is greater thanthe refractive index of the diameter direction (rectangular direction).The liquid crystal modulators in TN mode (or TN-type) are configured toapply only a half wavelength of retardation to a predeterminedwavelength of light in a state where voltage is not applied to theliquid crystal layer.

FIG. 1 is model diagram of the state of a liquid crystal layer, using atransmissive liquid crystal modulator in TN mode, without voltage beingapplied, and FIG. 2 is a model diagram of the state of a liquid crystallayer, using a transmissive liquid crystal modulator in TN mode, with apredetermined amount of voltage being applied.

The transmissive liquid crystal modulator comprises a transparentsubstrate 101, a facing transparent substrate 102, and a liquid crystallayer 10a0 a which contains liquid crystal molecules 100 sealed inbetween these two substrates.

The transparent substrate 101 comprises a transparent pixel electrode104 arranged in a matrix of rows and columns not shown, for exampleformed of an ITO (indium tin oxide), a liquid crystal oriented film 106formed of for example a polyimide polymer, a switching device 103 forelectrically driving the pixel electrode 104, and wiring not shown, andthe pixel electrode 104 is configured so as to be individually drivenelectrically.

Also, the facing transparent substrate 102 can be formed of atransparent common electrode 105 formed from for example an ITO (indiumtin oxide), and a liquid crystal oriented film 107 formed of for examplea polyimide polymer.

Next, the operation of the transmissive liquid crystal modulator will bedescribed. In FIG. 1, the light LIW from the light source is cast in thedirection of the arrow IW in the diagram as linear polarization with thepolarization direction being a 45 degree angle from the orienteddirection of the substrate boundary of the liquid crystal molecules 100,via a polarization selecting device not shown. The incident light LIW isdivided into two characteristic modes and propagates and transits theliquid crystal layer 100 a, and is emitted in the direction of the arrowOW in the diagram as light LOW.

At this time, retardation Δ is generated between the two modes in theliquid crystal layer 100 a, which is expressed by the followingExpression.Δ=d·Δn  (5)

In the Expression (5), d is the thickness of the liquid crystal layer100 a, and Δn is the refractive index anisotropy of the liquid crystallayer.

Thus the transmittance T(λ) of the light with components which areorthogonal to the linear polarization of the incident light LIW to becast into the transmissive liquid crystal modulator is as follows. Ifthe aperture ratio of the transmissive liquid crystal modulator is 100%and the non-polarized transmittance is 100%, then the lighttransmittance T(λ) when the light is emitted in the direction of thearrow OW as to the retardation Δ isT(λ)=0.5(1−cos(2πΔ/λ))  (6)

where λ is the wavelength of the incident light.

In other words, the transmittance T(λ) is dependent on the wavelength ofthe incident light λ and the retardation Δ which the liquid crystaldevices themselves apply. When the retardation Δ is λ/2, then T(λ)=1,and transmittance is greatest, and the state in which the retardation Δdoes not apply voltage to the liquid crystals, that is to say thesituation in FIG. 1 is greatest, and retardation Δ cannot be increasedfurther.

FIG. 2 illustrates the state in FIG. 1 with a situation where theelectrical field of the dotted line arrow 108 in the diagram is appliedbetween the transparent electrodes 104 and 105.

The liquid crystal molecules 100 are in a state of being slightly tiltedin the direction of the liquid crystal layer thickness due toapplication of an electric field. By tilting the major axis directionhaving the molecule refractive index anisotropy of the liquid crystalmolecules 100 towards the light transmitting direction, the apparentrefractive index anisotropy Δn can be reduced with respect to ahorizontal wave.

In other words, by applying voltage to the liquid crystal, the state inFIG. 2 shows a state where the retardation Δ expressed in Expression (5)is decreased compared to the state in FIG. 1.

On the other hand, the light spectrum which breaks out the three primarycolors (RGB-colors) and illuminates the liquid crystal modulators isbroken out into the R-color (solid line), G-color (dotted line), andB-color (broken line) as illustrated in FIG. 7, when using an ultra highpressure mercury lamp for a light source, for example.

The center-of-gravity wavelength (center wavelength) of the wavelengthband for each color is RC for the R-color, GC for the G-color, and BCfor the B-color.

Here the center-of-gravity wavelength λ0 refers to the wavelength of thehorizontal axis (wavelength) of the center-of-gravity of the areaenclosed by the curved lines of the wavelength band for each color lightin FIG. 7. Alternatively, a representative wavelength for each color cansimply be selected and these can be used as the center-of-gravitywavelength described above.

In the state shown in FIG. 1 where voltage is not applied to the liquidcrystal, the liquid crystal modulators are configured in the thickness dof the liquid crystal layer 100 a and the refractive index anisotropy Δnof the liquid crystal layer 100 a so as to apply retardation ofΔR=RC/2=d·Δn of half wavelength (e.g., within the range of plus or minus5%) as to the wavelength of the center-of-gravity wavelength RC in theR-color wavelength range which has the longest wavelength among thethree primary colors. Then, the liquid crystal modulators (liquidcrystal panel) for R-color modulation performs modulation to the R-colorlight by adjusting the applied voltage for each pixel within the rangefrom the state of no voltage applied (that is to say, the state ofapplying retardation of an approximate half wavelength to the R-colorlight) to the state where voltage is applied so that the refractiveindex anisotropy Δn becomes almost 0.

Modulation of the G-color light is performed on the G-color modulationliquid crystal panel, as illustrated in FIG. 7, by adjusting the appliedvoltage for each pixel within the range of the state where only enoughvoltage is applied to the liquid crystal for the retardation Δ to behalf wavelength (e.g., within the range of plus or minus 5%) as to thecenter-of-gravity wavelength GC of the G-color wavelength band (appliedvoltage EG), to the state where voltage is applied so that therefractive index anisotropy Δn becomes almost 0 (applied voltage EGO).

Further, modulation of the B-color light is performed on the B-colormodulation liquid crystal panel, by adjusting the applied voltage foreach pixel within the range of the state where only enough voltage isapplied to the liquid crystal for the retardation Δ to be halfwavelength (e.g., within the range of plus or minus 5%) as to thecenter-of-gravity wavelength BC of the B-color wavelength band (appliedvoltage EB), to the state where voltage is applied so that therefractive index anisotropy Δn becomes almost 0 (applied voltage EBO).

With such a configuration, the efficiency of light use can be improvedwithout loss of R-color transmittance which has the longest wavelengthband (without loss of the amount of R-color light within the displayedimage, or while reducing color balance distortion from the reduction ofthe amount of R-color light within the displayed image, or whilelowering the degree of loss of the amount of light or lowering of theamount of R-color light or of color balance distortion based thereon,within the displayed image). Also, deterioration of color purity can bereduced by shifting the R-color wavelength band toward G (or expandingtoward G) to adjust the color balance.

Also, with the present exemplary embodiment, the greatest retardationamount Δmax of the liquid crystal modulator can be set to the R-colorcenter-of-gravity wavelength (e.g., within the range of plus or minus5%), so the exemplary embodiment is not restricted to cases of using thesame liquid crystal modulators of all of the R, G, and B colormodulation, and liquid crystal modulators of the same configuration canbe used for modulation of R-color and G-color while an adjusting liquidcrystal modulator, which differs in configuration from the liquidcrystal modulators positioned in the light path of the R- and G-colorlights, can be used for the modulation of B-color. Specifically, liquidcrystal modulators can be used which apply a half wavelength of phasedifference with respect to the B-color center-of-gravity wavelengthwithout about any voltage being applied, and can change the appliedvoltage up to the state where the refractive index anisotropy Δn withrespect to the B-color center-of-gravity wavelength of the liquidcrystal modulators becomes almost 0.

Therefore, in at least one example, in order to suppress deteriorationof light resistance from short wavelength light with high photon energy,a liquid crystal with high light resistance or various polymers can beused only for the liquid crystal modulators for use with B-color lightmodulation.

Also for the G-color and B-color modulations liquid crystal modulatorswith the same configuration can be used. For the R-color modulation,liquid crystal modulators with a differing configuration from the liquidcrystal modulators thereof can be used. In such a case, the amount ofretardation applied in a state with no voltage applied to the R-colorliquid crystal modulators are half wavelength of the R-color lightcenter-of-gravity wavelength RC, and the amount of retardation appliedto the G-color light center-of-gravity wavelength GC in a state with novoltage applied to the G-color liquid crystal modulators is a halfwavelength of the G-color light center-of-gravity wavelength GC. In thiscase, these liquid crystal modulators have no voltage applied, andbecause a phase difference of half wavelength of the center-of-gravitywavelength BC is not applied to the center-of-gravity wavelength BC inthis state, for the G-color and B-color common liquid crystal modulatorswhich are positioned in the light path of the B-color light, controlscan be placed so that the retardation amount where a predeterminedvoltage is applied is a half wavelength of the B-color center-of-gravitywavelength BC.

Next, a reflective liquid crystal modulator will be described.

FIG. 3 is a model diagram of a state of a liquid crystal layer, using areflective liquid crystal modulator in TN mode, without voltage beingapplied, and FIG. 4 is a model diagram of a state of a liquid crystallayer, using a reflective liquid crystal modulator in TN mode, with apredetermined amount of voltage being applied.

The reflective liquid crystal modulator comprises a silicon substrate201, a facing transparent substrate 202, and a liquid crystal layer 200a which contains liquid crystal molecules 200 sealed in between thesetwo substrates.

The silicon substrate 201 comprises: a mirror pixel electrode 204, whichhas been formed (e.g., from aluminum) and finished to be mirror-like,arranged in a matrix of rows and columns not shown; a liquid crystaloriented film 206 formed of for example a polyimide polymer, and aswitching circuit layer 203 containing a switching device 203 formed ofa MOSFET for electrically driving the mirror pixel electrode 204; andthe mirror pixel electrode 204 which can be configured so as to beindividually driven electrically.

Also, the facing transparent substrate 202 (liquid crystal layer side)can be formed of a transparent common electrode 205 formed from forexample an ITO (indium tin oxide), and a liquid crystal oriented film207 formed of for example a polyimide polymer.

Next, the operation of the reflective liquid crystal modulator will bedescribed. In FIG. 3, the light LIW from the light source is cast in thedirection of the arrow IW in the diagram as linear polarization with thepolarization direction being a 45 degree angle from the orienteddirection of the substrate boundary of the liquid crystal molecules 100,via a polarization selecting device not shown. The incident light LIW isdivided into two characteristic modes and propagates and reflects at theliquid crystal layer 200 a, and is emitted in the direction of the arrowOW in the diagram as light LOW. At this time, retardation Δ is generatedbetween the two modes in the liquid crystal layer 200 a, which isexpressed with the following Expression.Δ=2s·Δn  (7)

In Expression (7), d is the thickness of the liquid crystal layer, andΔn is the refractive index anisotropy of the liquid crystal layer 200 a.Thus, of the light which reflects back from the mirror pixel electrode204 of the reflective-type liquid crystal modulator, and is emittedtherefrom, the reflectivity R(λ) of the light with components which areorthogonal to the linear polarization of the incident light LIW is asfollows.

If the aperture ratio of the reflective liquid crystal modulators is100% and the non-polarized reflectivity is 100%, then the reflectivityR(λ) of the light emitted in the arrow OW direction as to theretardation λ isR(λ)=0.5(1−cos(2πΔ/λ))  (8)

Here, λ is the wavelength of the incident light. In other words, as withthe example of the transmissive liquid crystals, the reflectivity R(λ)is dependent on the incident light wavelength λ, as to the retardation Δapplied by the liquid crystal devices themselves. When the retardation Δis λ/2, then R(λ)=1, and the greatest reflection is obtained, and alsothe situation where the retardation Δ does not apply any voltage to theliquid crystals, that is to say the situation in FIG. 3 is at itsgreatest, and the retardation Δ cannot be increased any further.

FIG. 4 illustrates the state in FIG. 3 with a situation where theelectrical field of the dotted line arrow 208 in the diagram is appliedbetween the transparent electrodes 204 and 205.

The liquid crystal molecules 200 are in a state of being slightly tiltedin the direction of the liquid crystal layer thickness. By tilting themajor axis direction having the molecule refractive index anisotropy ofthe liquid crystal molecules 200 towards the light reflecting direction,the apparent refractive index anisotropy Δn can be decreased as to ahorizontal wave. In other words, by applying voltage to the liquidcrystal, the state in FIG. 4 shows a state where the retardation Δexpressed in Expression (7) is decreased compared to the state in FIG.3.

Thus, in the state shown in FIG. 3 where voltage is not applied to theliquid crystal, the liquid crystal modulators are configured in thethickness d of the liquid crystal layer 200 a and the refractive indexanisotropy Δn of the liquid crystal layer 200 a so as to applyretardation Δ of ΔR=RC/2=d·Δn of half wavelength as to the wavelength ofthe center-of-gravity wavelength (central wavelength) RC in the redcolor wavelength range which has the longest wavelength among the threeprimary colors.

The liquid crystal panel for red color modulation performs reflectivemodulation within the range from the state of no voltage applied to thestate where voltage is applied so that the refractive index anisotropyΔn becomes almost 0. Reflective modulation is performed on the G-colormodulation liquid crystal panel, as illustrated in FIG. 4, within therange of the state where only enough voltage is applied to the liquidcrystal for the retardation Δ to be half wavelength as to thecenter-of-gravity wavelength GC of the G-color wavelength band, to thestate where voltage is applied so that the refractive index anisotropyΔn becomes almost 0.

Further, reflective modulation can be performed on the B-colormodulation liquid crystal panel, within the range of the state whereonly enough voltage is applied to the liquid crystal for the retardationΔ to be half wavelength as to the center-of-gravity wavelength BC of theB-color wavelength band, to the state where voltage is applied so thatthe refractive index anisotropy Δn becomes almost 0. Thus, theefficiency of light use can be improved without loss of R-colorreflectivity which has the longest wavelength band, and for adjustingthe color balance, the R-color wavelength band is shifted to the G-sideand thus prevents deterioration of color purity.

Also, as with the example of the transmissive liquid crystal describedabove, the present exemplary embodiment can set the greatest retardationamount Δmax of the liquid crystal modulators to the red colorcenter-of-gravity wavelength, and therefore the same liquid crystalmodulators can be used for modulation of R-color and G-color, not onlyin the cases using the same liquid crystal modulators of a substantialportion (e.g., all) of the R, G, and B color modulations.

In this instance, there is the advantage wherewith, in order to suppressdeterioration of light resistance from short wavelength light with highphoton energy, liquid crystal with high light resistance or variouspolymers can be used exclusively for the liquid crystal modulators foruse with B-color light modulation.

Thus, the liquid crystal modulators according to the present exemplaryembodiment are positive nematic modulators with TN mode action, and thethree liquid crystal modulators are formed with the same construction,and the amount of retardation applied to the liquid crystal modulatorswhen no voltage is applied equates to a half-wavelength of theapproximate center wavelength in the light wavelength band with thelongest wavelength of the three colored lights. The two liquid crystalmodulators which modulate the remaining two colored lights can applyretardation equating to a half-wavelength of the approximate centerwavelength of the light wavelength band of each color light, withapplication of the predetermined voltage.

Now, in the case that the three liquid crystal modulators are formedwith the same construction, specifically the construction can be asdescribed below. With an image display device which performs display besynthesizing image light from the three liquid crystal modulators, i.e.,a first liquid crystal modulator for modulating the polarization stateof a first colored light (e.g., R-color), a second liquid crystalmodulator for modulating the polarization state of a second coloredlight (e.g., G-color) which can have a shorter wavelength than the firstcolored light, and a third liquid crystal modulator for modulating thepolarization state of a third colored light (e.g., B-color) which canhave a shorter wavelength than the second colored light, where the threeliquid crystal modulators are TN-type liquid crystal modulators. Forexample, a first voltage can be applied to the first liquid crystalmodulator for half-wavelength retardation of the first colored light, asecond voltage which is higher than the first voltage can be applied tothe second liquid crystal modulator for half-wavelength retardation ofthe second colored light, and a third voltage which is higher than thesecond voltage can be applied to the third liquid crystal modulator forhalf-wavelength retardation of the third colored light. Also, theconfiguration of an image display device of a same configuration, wherethe three liquid crystal modulators are TN-type liquid crystalmodulators, can be such that the retardation which the second liquidcrystal modulator applies to incident light (e.g., first colored light)without applying voltage is less than the retardation which the firstliquid crystal modulator applies to incident light (e.g., first coloredlight) without applying voltage, and the retardation which the thirdliquid crystal modulator applies to incident light (e.g., first coloredlight) without applying voltage is less than the retardation which thesecond liquid crystal modulator applies to incident light (e.g., firstcolored light) without applying voltage.

In addition to this, with the three liquid crystal modulators accordingto the present exemplary embodiment, of the three colored light to bemodulated, when the liquid crystal modulators which modulate the lightin order of shortest wavelength can be defined as liquid crystalmodulator B, G, R, the two liquid crystal modulators G and R are formedwith the same construction, and the liquid crystal modulator B is formedwith a construction differing from the other two liquid crystalmodulators G and R. Additionally, the amount of retardation applied tothe liquid crystal modulator B when there is no voltage applied equatesto a half-wavelength of the approximate center wavelength of theshortest light wavelength band of the three colored lights. Furthermorethe amount of retardation applied to the liquid crystal modulator R whenthere is no voltage applied equates to a half-wavelength of theapproximate center wavelength of the longest light wavelength band ofthe three colored lights, and the retardation applied to the liquidcrystal modulator G equating to a half-wavelength of the approximatecenter wavelength of an intermediate colored light wavelength band isapplied according to the predetermined voltage application.

Thus, when the liquid crystal modulators for G and R are of the sameconstruction, and the liquid crystal modulators for B differs fromthose, specifically the construction can be as described below. Forexample, with an image display device which performs display bysynthesizing image light from the three liquid crystal modulators, i.e.,a first liquid crystal modulator for modulating the polarization stateof a first colored light, a second liquid crystal modulator formodulating the polarization state of a second colored light, which has ashorter wavelength than the first colored light, and a third liquidcrystal modulator for modulating the polarization state of a thirdcolored light which has a shorter wavelength than the second coloredlight. Where the three liquid crystal modulators are TN-type liquidcrystal modulators, the retardation which the first liquid crystalmodulator applies to incident light (e.g., first colored light) withoutapplying voltage is about the same as the retardation which the secondliquid crystal modulator applies to incident light (e.g., first coloredlight) without applying voltage, and the retardation which the first andsecond liquid crystal modulator applies to incident light (e.g., firstcolored light) without applying voltage is greater than the retardationwhich the third liquid crystal modulator applies to incident light(e.g., first colored light) without applying voltage.

In addition to this, with the two liquid crystal modulators according tothe present exemplary embodiment, the two liquid crystal modulators Gand B can be formed with the same construction, and the liquid crystalmodulator R can be formed with a construction differing from the othertwo liquid crystal modulators G and B. Additionally, the amount ofretardation applied to the liquid crystal modulator R when there is novoltage applied equates to a half-wavelength of the approximate centerwavelength of the light wavelength band with the shortest wavelength ofthe three colored lights. Furthermore, the amount of retardation appliedto the liquid crystal modulator G when there is no voltage appliedequates to a half-wavelength of the approximate center wavelength of anintermediate colored light wavelength band of the three colored lights,and the retardation applied to the liquid crystal modulator B equatingto a half-wavelength of the approximate center wavelength of the lightwavelength band with the shortest wavelength is applied according to thepredetermined voltage application.

Thus, an exemplary embodiment where the liquid crystal modulators for Band G are of the same construction, and the liquid crystal modulatorsfor R differs from those, are described below. For example, with animage display device synthesizing image light from the three liquidcrystal modulators, comprising a first liquid crystal modulator formodulating the polarization state of a first colored light, a secondliquid crystal modulator for modulating the polarization state of asecond colored light which has a shorter wavelength than the firstcolored light, and a third liquid crystal modulator for modulating thepolarization state of a third colored light which has a shorterwavelength than the second colored light. The three liquid crystalmodulators are TN-type liquid crystal modulators, the retardation whichthe first liquid crystal modulator applies to incident light (e.g.,first colored light) without applying voltage is greater than theretardation which the second liquid crystal modulator applies toincident light (e.g., first colored light) without applying voltage. Theretardation which the second liquid crystal modulator applies toincident light (e.g., first colored light) without applying voltage isabout the same as the retardation which the third liquid crystalmodulator applies to incident light (e.g., first colored light) withoutapplying voltage.

Now, the “same construction” here has the meaning that for the samewavelengths of light without voltage being applied, about the sameretardation (phase difference) is applied, and about the sameretardation is applied to the same wavelengths in a state with apredetermined voltage applied. In other words, even if the outwardappearance is slightly different, the construction can be the same.

The present exemplary embodiment is not restricted to the abovedescription. For example, the liquid crystal modulators R, G, and B canall have structures different one from another. That is to say, theliquid crystal modulators can each be configured to provide differentretardation (optical path difference) to incident light (light of anywavelength is permissible, for example light within the visible lightrange). Specifically, a configuration is made where retardation (opticalpath difference) which the liquid crystal modulator R provides toincident light (light of any wavelength is permissible, for examplelight within the visible light range) without voltage being applied isgreater than the retardation which the liquid crystal modulator Gprovides to incident light without voltage being applied. Retardationwhich the liquid crystal modulator G provides to incident light withoutvoltage being applied is greater than the retardation which the liquidcrystal modulator B provides to incident light without voltage beingapplied. Note that “retardation” as used here refers to the optical pathdifference of two light rays of which the polarization directions aremutually orthogonal, and even if the optical path difference is aboutthe same (structure is about the same), difference in the wavelength ofthe light to which the optical path difference is provided consequentlyresults in difference in the provided phase difference.

In this case, the phase difference which the liquid crystal modulator Rprovides to the R colored light (representative wavelength of R coloredlight or wavelength region of R colored light) without voltage beingapplied, the phase difference which the liquid crystal modulator Gprovides to the G colored light (representative wavelength of G coloredlight or wavelength region of G colored light) without voltage beingapplied, and the phase difference which the liquid crystal modulator Bprovides to the B colored light (representative wavelength of B coloredlight or wavelength region of B colored light) without voltage beingapplied, are about the same (e.g., one can be 95% or more or 105% orless of another, or for example 98% or more or 102% or less), with thephase difference being generally half-wave. However, in the event ofactually providing half-wave phase difference to the colored light,minute voltage can be applied to the liquid crystal modulators.

Thus, the configuration features of the image display device accordingto the present exemplary embodiment are as follows.

The image display device comprises a first liquid crystal modulator formodulating the polarization state of a first colored light, a secondliquid crystal modulator for modulating the polarization state of asecond colored light which has a shorter wavelength than the firstcolored light, and a third liquid crystal modulator for modulating thepolarization state of a third colored light which has a shorterwavelength than the second colored light, and synthesizes image lightfrom the three liquid crystal modulators and displays this.

The features of at least one exemplary embodiment thereof are that:

the three liquid crystal modulators are TN-type liquid crystalmodulators,

in order to apply a half-wavelength retardation (retardation equivalentto half-wave length of the first colored light) to the first coloredlight, the first voltage is applied to the first liquid crystalmodulator. In order to apply a half-wavelength retardation (retardationequivalent to half-wave length of the second colored light) to thesecond colored light, a second voltage which is greater than the firstvoltage is applied to the second liquid crystal modulator. In order toapply a half-wavelength retardation (retardation equivalent to half-wavelength of the third colored light) to the third colored light, a thirdvoltage which is greater than the second voltage is applied to the thirdliquid crystal modulator, that is to say, in this case, the three liquidcrystal modulators are about the same structure.

the retardation which the second liquid crystal modulator applies toincident light (e.g., first colored light) without applying voltage isless than the retardation which the first liquid crystal modulatorapplies to incident light (e.g., first colored light) without applyingvoltage, and the retardation which the third liquid crystal modulatorapplies to incident light (e.g., first colored light) without applyingvoltage is less than the retardation which the second liquid crystalmodulator applies to incident light (e.g., first colored light) withoutapplying voltage, that is to say, in this case, the three liquid crystalmodulators all are of different structures.

the retardation which the first liquid crystal modulator applies toincident light (e.g., first colored light) without applying voltage isabout the same as the retardation which the second liquid crystalmodulator applies to incident light (e.g., first colored light) withoutapplying voltage, and the retardation which the first and-second liquidcrystal modulator applies to incident light (e.g., first colored light)without applying voltage is greater than the retardation which the thirdliquid crystal modulator applies to incident light (e.g., first coloredlight) without applying voltage, that is to say, in this case, thestructure of the second liquid crystal modulator and the structure ofthe third liquid crystal modulator are the same, while the structure ofthe first liquid crystal modulator is different from these structures.

the retardation which the first liquid crystal modulator applies toincident light (e.g., first colored light) without applying voltage isgreater than the retardation which the second liquid crystal modulatorapplies to incident light (e.g., first colored light) without applyingvoltage, and the retardation which the second liquid crystal modulatorapplies to incident light (e.g., first colored light) without applyingvoltage is about the same as the retardation which the third liquidcrystal modulator applies to incident light (e.g., first colored light)without applying voltage, that is to say, in this case, the structure ofthe first liquid crystal modulator and the structure of the secondliquid crystal modulator are the same, while the structure of the thirdliquid crystal modulator is different from these structures.

a first voltage is applied to the first liquid crystal modulator forhalf-wavelength retardation of the first colored light, a second voltagewhich is higher than the first voltage is applied to the second liquidcrystal modulator for half-wavelength retardation of the second coloredlight, a third voltage which is higher than the second voltage isapplied to the third liquid crystal modulator for half-wavelengthretardation of the third colored light.

Thus, a liquid crystal projection-type image display device with animage display with a bright, wide color range can be achieved.

Next, a first exemplary embodiment of the projection-type display deviceaccording to at least one exemplary embodiment will be described basedon FIG. 8. FIG. 8 is a cross-sectional view of a primary optical systemcomprising the first exemplary embodiment of the projection-type displaydevice.

In FIG. 8, a drive signal from a light modulator panel driver 3, whichconverts an external video input signal not shown into a lightmodulation panel drive signal, independently controls each of a redlight modulation panel 2R, a green light modulation panel 2G, and a bluelight modulation panel 2B, which are formed from transmissive liquidcrystal modulators via the solid lines in the diagram.

At this time, the voltage to be applied to each light modulator panel2R, 2G, and 2B are controlled as described above.

On one hand, illumination which is a linearly polarized wave in thevertical direction in the diagram from an illumination device 1 (sideview is shown horizontally) first deflects a red color component R witha dichroic mirror 20 for separating the red-cyan wavelength band, whichreflects the color red and transmits the color cyan (green and blue),and the deflected red color R is guided to the red light modulationpanel 2R with a total reflection mirror 22. On the other hand, cyancolor component transmitted and separated by the dichroic mirror 20 forseparating and transmitting the red-cyan wavelength band deflects agreen color component of the yellow component of the color cyan with adichroic mirror 21 for separating the yellow-blue wavelength band, whichreflects the color yellow and transmits the color blue B, and thedeflected green color G is guided to the green light modulation panel2G. Also, the blue color component B transmitted and separated by thedichroic mirror 21 for yellow-blue wavelength band is guided to the bluelight modulation panel 2B with total reflection mirrors 23 and 24. Atthis time, in order to extend the light path length, a cats-eye opticalsystem using Fourier transformation lenses 25 and 26 transfers the pupilto the light modulation panel 2B.

With the above illumination configuration, the red light modulationpanel 2R, the green light modulation panel 2G, and the blue lightmodulation panel 2G are illuminated.

On the other hand, the linearly polarized illumination which ispolarized in the vertical direction in the diagram with the red lightmodulation panel 2R, the green light modulation panel 2G, and the bluelight modulation panel 2B, which are modulated according to the videosignal, have retardation applied to the polarized light thereofaccording to the modulation state of the pixels arranged in the redlight modulation panel 2R, the green light modulation panel 2G, and theblue light modulation panel 2B.

Of the light flux modulated in the red light modulation panel 2R, thegreen light modulation panel 2G, or the blue light modulation panel 2B,affixed to the incidence surface for each color of the cross dichroicprism 12, the modulated light components polarized in the verticaldirection in the diagram by a red analyzer 27, a green analyzer 28, or ablue analyzer 29 respectively, are transmitted, and the modulated lightcomponents polarized in the horizontal direction in the diagram areabsorbed in the analyzers and disappear as heat (note that an analyzeris an optical device which shields light of a different polarizationstate from that of the image light so as to not enter the projectionoptical system, examples thereof being polarization plates, beamsplitters). Hereafter the modulated light components polarized in thevertical direction in the diagram which have been modulated with eachcolor are cast in the cross dichroic prism 12.

The cross dichroic prism 12 can be configured with a red-reflectivedichroic wavelength band separation film 12R for the S-polarized light,for reflecting the red color R and transmitting the green color G andthe blue color B, and a blue-reflective dichroic wavelength bandseparation film 12B for reflecting the blue color B and transmitting thegreen color G and the red color R, which can be arranged in a crosspattern.

Therefore green has the feature of independently transmitting thered-reflective dichroic wavelength band separation film 12R and theblue-reflective dichroic wavelength band separation film 12B. By usingthe cross dichroic prism 12, the image information light of the redcolor R is deflected in the direction of the projection lens 4 by thered-reflective dichroic wavelength band separation film 12R, the imageinformation light of the blue color B is deflected in the direction ofthe projection lens 4 by the blue-reflective dichroic wavelength bandseparation film 12B, and the image information light of the green colorG advances in the direction of the projection lens 4 without beingdeflected.

However, the multiple pixels arranged on the red light modulation panel2R, green light modulation panel 2G, and blue light modulation panel 2Bcan be adjusted or mechanically or electrically compensated so as tohave predetermined pixels overlap relative to each other with apredetermined degree of precision.

Next, the lights R, G, B which have been modulated as multiplexedcolored light are captured by the entrance pupil of the projection lens4 in that state, and the light modulation face of each of the red lightmodulation panel 2R, green light modulation panel 2G, and blue lightmodulation panel 2G and the light diffusion face of a light diffusionscreen 5 can be arranged in optically coupled relationships by theprojection lens 4, and therefore are transferred to the light diffusionscreen 5, and the image according to the video signal is displayed onthe light diffusion screen 5.

A second exemplary embodiment of the projection-type display deviceaccording to the present exemplary embodiment will be described based onFIG. 9. FIG. 9 is a cross-sectional view of the main optical systemcomprising the second exemplary embodiment of the projection-typedisplay device.

In FIG. 9, a drive signal from a light modulation panel drive 3 whichconverts an external video input signal, not shown, to a lightmodulation panel drive signal independently controls each of the redlight modulation panel 2Rb, green light modulation panel 2Gb, and bluelight modulation panel 2Bb which are formed of reflective liquid crystalmodulators via the solid line in the diagram, and on one hand.Illumination which is a linearly polarized wave in the verticaldirection in the diagram from an illumination device 1 (side view isshown horizontally) first deflects a magenta color component R with adichroic mirror 30 for separating the magenta-green wavelength band,which reflects the color magenta (red and blue) and transmits the colorgreen G, and the deflected color magenta transits the blue cross colorpolarizer 34 applying half-wavelength retardation to the blue polarizedlight. Thus, the blue color component B which is linearly polarized inthe horizontal direction in the diagram and the red color component Rwhich is linearly polarized in the vertical direction in the diagram arecreated, and next, are cast into a polarizing beam splitter 33. The bluecolor component B which is linearly polarized in the horizontaldirection in the diagram transmits the polarization separation film 33 abecause of a P-polarizing wave, and is guided to the blue lightmodulation panel 2B. The red color component R, which is linearlypolarized in the vertical direction in the diagram, reflects off thepolarization separation film 33 a because of a S-polarizing wave, and isguided to the red light modulation panel 2R.

On the other hand, the green color component G, which is transmitted andseparated by the magenta-green wavelength band separation dichroicmirror 30, transits a dummy glass 36 for the purpose of correcting thelight path, and next is cast into a polarizing beam splitter 31. Thegreen color component G which is linearly polarized in the verticaldirection in the diagram reflects off the polarization separation film31 a because of a S-polarizing wave, and is guided to the green lightmodulation panel 2G.

With the above illumination configuration, the red light modulationpanel 2R, green light modulation panel 2G, and blue light modulationpanel 2G are illuminated.

On the other hand, the light which illuminates each of the lightmodulation panels 2R, 2G, and 2B with the red light modulation panel 2R,green light modulation panel 2G, blue light modulation panel 2G whichare modulated according to the video signal have retardation applied tothe polarized light thereof according to the modulation state of thepixels arranged in the red light modulation panel 2R, green lightmodulation panel 2G, and blue light modulation panel 2B.

The polarized light components, in the same direction as theillumination, return to the light source lamp side, following the lightpath which approximately turns back the illumination light path. Thepolarized light components, at right angles to the polarizationdirection of the illumination, includes the modulated light by the redlight modulation panel 2R in the horizontal direction in the diagram,and transits the polarization separation film 33 a because of aP-polarizing wave, and transits a red cross color polarized light 35which applies half-wavelength retardation to the red polarized light.Then, the polarized light components are converted to a red colorcomponent R which is linearly polarized in the vertical direction in thediagram, and next is cast into a polarizing beam splitter 32, and thered color component R which is linearly polarized in the verticaldirection in the diagram reflects off the polarization separation film32 a because of a S-polarizing wave, and is deflected in the directionof the projection lens 4.

The modulated light by the blue light modulation panel 2B is polarizedso that the polarization direction is in the vertical direction in thediagram, and reflects off the polarization separation film 33 a of thepolarizing beam splitter 33 because of a S-polarizing wave. Themodulated light from the blue light modulation panel then transitswithout any action by a red cross color polarizer 35 which applies thehalf-wavelength retardation to the red color R polarized light, and nextis cast into a polarizing beam splitter 32, and the blue color componentB which is linearly polarized in the vertical direction in the diagramreflects off the polarization separation film 32 a because of aS-polarizing wave, and is deflected in the direction of the projectionlens 4.

The modulated light by the green light modulation panel 2G is polarizedso that the polarization direction is in the horizontal direction in thediagram, and transmits the polarization separation film 32 a of thepolarizing beam splitter 31 because of a P-polarizing wave. Themodulated light by the green light modulation panel then transits adummy glass 37 for the purpose of correcting the light path, and next iscast into the polarizing beam splitter 32, and the green color componentG, which is linearly polarized in the horizontal direction in thediagram, transmits the polarization separation film 32 a because of aP-polarizing wave, and is guided in the direction of the projection lens4. However, the multiple pixels arranged on the red light modulationpanel 2R, green light modulation panel 2G, and blue light modulationpanel 2B are adjusted or mechanically or electrically compensated so asto have predetermined pixels overlap relative to each other with apredetermined degree of precision.

Next, the lights R, G, B which have been modulated as multiplexedcolored light are captured by the entrance pupil of the projection lens4 in this state, and since the light modulation face of each of the redlight modulation panel 2R, green light modulation panel 2G, and bluelight modulation panel 2G and the light diffusion face of a lightdiffusion screen 5 can be arranged in an optically cooperativerelationship by the projection lens 4, the multiplexed colored light istransferred to the light diffusion screen 5, and the image according tothe video signal is displayed on the light diffusion screen 5.

As described above, according to the various exemplary embodiments,liquid crystal modulators (modulation liquid crystal panels) in thethree primary colors do not need to be separately formed individualitems, and a liquid crystal projection-type image display device with abright, wide color range can be provided easily without loss ofefficiency of use of the red color light which has the longestwavelength or the green color light.

With the exemplary embodiments described above, liquid crystalmodulators which apply approximately half-wavelength retardation when novoltage is applied have been described, but the present invention is notrestricted to these. For example, a liquid crystal modulationconfiguration can be used where there is about no retardation in a statewith no voltage applied, and retardation is only applied to incidentlight when voltage is applied. In this case, with a liquid crystaldisplay device using transmittance liquid crystal modulators (a liquidcrystal projector), if the polarization direction aligned by the liquidcrystal modulators (the polarization direction of transmittance of thepolarization substrate on the incident side of the liquid crystalmodulators) and the polarization direction of transmittance of thepolarization substrate on the emitting side of the liquid crystalmodulators are parallel, the display is white where there is no voltageapplied, and conversely, with a transmissive type liquid crystalprojector, if the polarization direction of transmittance of thepolarization substrate on the incident side of the liquid crystalmodulators and the polarization direction of transmittance of thepolarization substrate on the emitting side of the liquid crystalmodulators are perpendicular, the display is black where there is novoltage applied. Also, with a liquid crystal display using reflectiveliquid crystal modulators (liquid crystal projector), in the event apolarizing beam splitter is positioned in the position which correspondsto the liquid crystal modulators, the display is black where there is novoltage applied. However, even in such an event, if a quarter-wavelengthsubstrate is appropriately positioned between the reflective liquidcrystal modulators and the polarizing beam splitter, the display can bewhite where there is no voltage applied.

In other words, the present exemplary embodiment can be applicable tovarious liquid crystal display devices, for example regardless ofwhether a liquid crystal display device which displays white where thereis no voltage applied, or a liquid crystal display device which displaysblack where there is no voltage applied, or a liquid crystal displaydevice which uses reflective liquid crystal modulators, or a liquidcrystal display device using transmissive liquid crystal modulators withwhich the polarization direction has about no change where there is novoltage applied, or a liquid crystal display device using liquid crystalmodulators which rotate the polarization direction 90 degrees wherethere is no voltage applied.

This application claims priority from Japanese Patent Application No.2005-074668 filed Mar. 16, 2005, which is hereby incorporated byreference herein in its entirety.

1. An image display device comprising: a first TN liquid crystalmodulator for modulating the polarization state of a first coloredlight; a second TN liquid crystal modulator for modulating thepolarization state of a second colored light which has a shorterwavelength than the first colored light; a third TN liquid crystalmodulator for modulating the polarization state of a third colored lightwhich has a shorter wavelength than the second colored light; and anoptical system for synthesizing the image light which is emitted fromthe three liquid crystal modulators, wherein a first voltage is appliedto the first liquid crystal modulator for providing the first coloredlight with about a half-wavelength phase difference, and wherein asecond voltage which is higher than the first voltage is applied to thesecond liquid crystal modulator for providing the second colored lightwith about a half-wavelength phase difference, and wherein a thirdvoltage which is higher than the second voltage is applied to the thirdliquid crystal modulator for providing the third colored light withabout a half-wavelength phase difference.
 2. An image display devicecomprising: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators, wherein theretardation which the second liquid crystal modulator applies toincident light without applying voltage is not equal to the retardationwhich the first liquid crystal modulator applies to incident lightwithout applying voltage, and wherein the retardation which the thirdliquid crystal modulator applies to incident light without applyingvoltage is not equal to the retardation which the second liquid crystalmodulator applies to incident light without applying voltage.
 3. Animage display device comprising: a first TN liquid crystal modulator formodulating the polarization state of a first colored light; a second TNliquid crystal modulator for modulating the polarization state of asecond colored light which has a shorter wavelength than the firstcolored light; a third TN liquid crystal modulator for modulating thepolarization state of a third colored light which has a shorterwavelength than the second colored light; and an optical system forsynthesizing the image light which is emitted from the three liquidcrystal modulators, wherein the retardation which the first liquidcrystal modulator applies to incident light without applying voltage isabout the same as the retardation which the second liquid crystalmodulator applies to incident light without applying voltage, andwherein the retardation which the first and second liquid crystalmodulator applies to incident light without applying voltage is greaterthan the retardation which the third liquid crystal modulator applies toincident light without applying voltage.
 4. An image display devicecomprising: a first TN liquid crystal modulator for modulating thepolarization state of a first colored light; a second TN liquid crystalmodulator for modulating the polarization state of a second coloredlight which has a shorter wavelength than the first colored light; athird TN liquid crystal modulator for modulating the polarization stateof a third colored light which has a shorter wavelength than the secondcolored light; and an optical system for synthesizing the image lightwhich is emitted from the three liquid crystal modulators, wherein theretardation which the first liquid crystal modulator applies to incidentlight without applying voltage is greater than the retardation which thesecond liquid crystal modulator applies to incident light withoutapplying voltage, and wherein the retardation which the second liquidcrystal modulator applies to incident light without applying voltage isabout the same as the retardation which the third liquid crystalmodulator applies to incident light without applying voltage.
 5. Animage display device comprising: a first TN liquid crystal modulator formodulating the polarization state of a first colored light; a second TNliquid crystal modulator for modulating the polarization state of asecond colored light which has a shorter wavelength than the firstcolored light; a third TN liquid crystal modulator for modulating thepolarization state of a third colored light which has a shorterwavelength than the second colored light; and an optical system forsynthesizing the image light which is emitted from the three liquidcrystal modulators, wherein in a state wherein the same voltage isapplied to the three liquid crystal modulators, the three liquid crystalmodulators are configured to apply about the same retardation as tolight of the same wavelength, and wherein the amount of retardation atthe time there is no voltage applied to the three liquid crystalmodulators equates to about a half-wavelength of approximate centerwavelength of the first colored light, and wherein the second and thirdliquid crystal modulators apply retardation equivalent to about ahalf-wavelength of approximate center wavelength of the second and thirdcolored lights, by applying a predetermined voltage on each of theliquid crystal modulators.
 6. An image display device comprising: afirst TN liquid crystal modulator for modulating the polarization stateof a first colored light; a second TN liquid crystal modulator formodulating the polarization state of a second colored light which has ashorter wavelength than the first colored light; a third TN liquidcrystal modulator for modulating the polarization state of a thirdcolored light which has a shorter wavelength than the second coloredlight; and an optical system for synthesizing the image light which isemitted from the three liquid crystal modulators, wherein in a statewherein a predetermined voltage is applied, the first and second liquidcrystal modulators are configured to apply about the same predeterminedretardation as to light of a predetermined wavelength, and wherein inthe state wherein the predetermined voltage is applied, the retardationwhich the third liquid crystal modulator applies as to light of thepredetermined wavelength differs from the predetermined retardation, andwherein the amount of retardation at the time there is no voltageapplied to the first liquid crystal modulator equates to about ahalf-wavelength of approximate center wavelength of the first coloredlight, and wherein the amount of retardation at the time there is novoltage applied to the third liquid crystal modulator equates to about ahalf-wavelength of approximate center wavelength of the third coloredlight, and wherein in order to apply the retardation equating to ahalf-wavelength of approximate center wavelength of the second coloredlight, a voltage greater than 0 (zero) is applied to the second liquidcrystal modulator.
 7. An image display device comprising: a first TNliquid crystal modulator for modulating the polarization state of afirst colored light; a second TN liquid crystal modulator for modulatingthe polarization state of a second colored light which has a shorterwavelength than the first colored light; a third TN liquid crystalmodulator for modulating the polarization state of a third colored lightwhich has a shorter wavelength than the second colored light; and anoptical system for synthesizing the image light which is emitted fromthe three liquid crystal modulators, wherein in a state wherein apredetermined voltage is applied, the second and third liquid crystalmodulators are configured to apply the same predetermined retardation asto light of a predetermined wavelength, and wherein in the state whereinthe predetermined voltage is applied, the retardation which the firstliquid crystal modulator applies as to light of the predeterminedwavelength differs from the predetermined retardation, and wherein theamount of retardation at the time there is no voltage applied to thefirst liquid crystal modulator equates to about a half-wavelength ofapproximate center wavelength of the first colored light, and whereinthe amount of retardation at the time there is no voltage applied to thesecond liquid crystal modulator equates to about a half-wavelength ofapproximate center wavelength of the second colored light, and whereinin order to apply the retardation equating to about a half-wavelength ofapproximate center wavelength of the third colored light, a voltagegreater than 0 (zero) is applied to the third liquid crystal modulator.8. The image display device according to claim 2, wherein theretardation which the second liquid crystal modulator applies toincident light without applying voltage is less than the retardationwhich the first liquid crystal modulator applies to incident lightwithout applying voltage, and wherein the retardation which the thirdliquid crystal modulator applies to incident light without applyingvoltage is less than the retardation which the second liquid crystalmodulator applies to incident light without applying voltage.
 9. Theimage display device according to claim 2, wherein the retardation whichthe second liquid crystal modulator applies to incident light withoutapplying voltage is greater than the retardation which the first liquidcrystal modulator applies to incident light without applying voltage,and wherein the retardation which the third liquid crystal modulatorapplies to incident light without applying voltage is greater than theretardation which the second liquid crystal modulator applies toincident light without applying voltage.